It is shown that in near-resonant $N$-photon ionization, chaotic light can be more efficient than purely coherent light by more than the usual factor of $N!$ ($N$ factorial). This occurs when the resonant intermediate state interferes with another nearby state. Specific results are presented for two-photon ionization.

• Received 23 March 1977

DOI:https://doi.org/10.1103/PhysRevLett.40.111